Maximum Safety at High Speeds

Today it is entirely possibly to purchase a road legal set of tyres rated for speeds above 185 miles per hour. Yet the faster a tyre’s rotation speed, the higher the resulting centrifugal acceleration will be. IN order to avoid the possibility of smoky scraps of shredded tread appearing in the rear view mirror, these UHP tyres must be designed to handle such extreme centrifugal forces. This can be accommodated by the use of jointless bandages composed of rubberised nylon or hybrid cords, which can absorb extremely high forces.

Tyre manufacturers traditionally produce these bandages through the calendering process. During the subsequent cutting process, however, the longitudinal knives employed can damage or even partially sever the bandage’s outer cords, compromising tyre quality. German companies KraussMaffei Berstorff and GfA De Pryck & Co mbH have worked collaboratively on the development of a means to produce jointless bandages that addresses this issue.

The cap strip line developed by the two firms is delivered ready to plug in and comprises of a rubber processing extruder with a downstream gear pump and hydraulic crosshead die. The die is capable of coating 128 cords at a time with a rubber compound and combining them to 16 cap strips that are subsequently wound around the belt during the tyre’s assembly.

KraussMaffei Berstorff and GfA not only provide the extruder and the control system technology; the offer a complete turnkey solution. The package on offer begins with the 128 spool creel, which can employ nylon or hybrid cords. It then continues to the extrusion line, which features a gear pump and hydraulic crosshead die, then up to the downstream equipment such, as cooling drum assembly, material accumulator and the 16-station winding system. The line achieves a throughput capacity of 40 m/min at constant output and delivers excellent extrudate homogeneity, reports KraussMaffei Berstorff.

The hydraulic crosshead die, the manufacturer continues, ensures shorter tooling times compared with the conventional die, screw connection version. As the final die is fixed by means of a hydraulic clamp, it can easily be replaced when changing the material. The crosshead is also equipped with a hydraulic opening and closing system that is said to make cleaning the unit a swifter process. Changing the creel takes just half an hour.

KraussMaffei Berstorff also notes that the wound-up spools can be changed at full operating speed. Thanks to the high degree of automation, the line can be run for up to ten hours without a pause.